1. Field of the Invention
The present invention relates to a CT scanning apparatus, and more particularly to a partial CT scanning apparatus suitable for partially radiographing tooth, jaw and face areas, for example.
2. Description of the Prior Art
A CT scanning apparatus generally comprises an X-ray source moving along a circular orbit around an object and an X-ray image pickup portion moving along a circular orbit on the opposite side of the X-ray source with respect to the object. In the image pickup portion, a line sensor arranged in a line or in a circular orbit detects X-rays passing through the object, and an X-ray image is built. In addition to this type of apparatus, an apparatus for carrying out radiographing by using a spiral orbit while an object placed on a bed is moved, and an apparatus for radiographing three-dimensional areas by using a two-dimensional image sensor, such as a TV camera, in its image pickup portion are also known.
In the case of these apparatuses, a blurred image is generated because of displacements of the X-ray source and the X-ray image pickup portion from their original orbits and movement of the object, even if the resolution of the image pickup system is raised. If the displacements from the orbits occur in the same pattern, the displacements can be corrected on the basis of the pattern when the image is built. However, if the displacements do not occur in the same pattern, correction is difficult. Furthermore, regarding the movement of the object, when the object is a living body in particular, the object itself may move during radiographing, and the so-called "moving artifact" occurs. To prevent this problem, the patient under test is required to be secured to a bed, for example. This further causes a problem of making the apparatuses larger in overall size.